Put simply, all Windows users, unless they're running Windows 95 in an underground Siberian bunker without access to the net, are going to need to update their systems.

Among these patches is a much anticipated fix for the zero-day vulnerability in Microsoft Word, which became the target of hacking attacks last month. There's also a cumulative security update for Internet Explorer, designed to fix four critical vulnerabilities affecting IE 5.0 and 6.0 on Windows 2000 and Windows XP/Windows Server 2003.

More info can be found in Microsoft's summary here or an overview by US CERT here. ®